Explain the Bioavailability of Folate?

Bioavailability of folate from naturally occurring food sources is variable and frequently incomplete, as mentioned earlier in the food sources section. The bioavailability of natural folates is affected by the removal of the polyglutamate chain by the intestinal conjugase. This process is apparently not complete, thereby reducing the bioavailability of natural folates by as much as 25-5096. In contrast, synthetic folic acid appears to be highly bio available- 85% or greater. The low bioavailability and, more importantly, the poor chemical stability of the natural folates have a profound influence on the development of nutrient recommendations. This is particularly true if some of the dietary intake is as stable and bio available as the synthetic fonn, folic acid. Fortification of foods such as breakfast cereals and flour can add significant amounts of folic acid to the diet.

Since folic acid (synthetic) taken with food is 85% bio available but food folate is only about 50% bio available, folic acid taken with food is 85150 (i.e. 1.7) times more  available. Thus, if a mixture of synthetic folic acid plus food folate bas been fed, dietary folate equivalents (DFEs) are calculated as follows to determine the EAR:

yg of DFE provided = [mg of food folate + (1.7 x mg of synthetic folic acid)].

To be comparable to food folate, only half as much folic acid is needed if taken on an empty stomach, i.e. lpg of DFE: = lmg of food folate = 0.5 mg of folic acid taken on an empty stomach = 0.6 mg of folic acid with meals.

Alcohol interferes with the absorption of folate and increases excretion of folate by the kidney.